Discharge lamp provided with a substantially straight oblong discharge tube

ABSTRACT

The invention relates to a discharge lamp provided with a substantially straight oblong discharge tube and an outer envelope surrounding this tube. The invention provides a solution in which a simple positioning of the discharge tube in the outer envelope can be obtained with the aid of an elongated part of the terminal wire. This solution is combined with an anti-shadow winding of that part of the terminal wire, which extends along the straight part of the discharge tube. By using this anti-shadow winding there need not be the risk of cracks in the outer envelope as a result of expansion of the terminal wire (by heat produced in the discharge tube).

United States Patent De Neve [451 Dec. 19, 1972 [54] DISCHARGE LAMP PROVIDED WITH A SUBSTANTIALLY STRAIGHT OBLONG DISCHARGE TUBE [72] Inventor: Gerard Marie Jules De Neve, Em-

masingel, Eindhoven, Netherlands [73] Assignee: U.S. Phillips York,N.Y.

221 Filed: March 1, 1971 21] Appl. No.: 119,488

Corporation, New

[30] Foreign Application Priority Data March 14, 1970 Netherlands ..7003667 [52] U.S. Cl. ..313/285, 313/220, 313/283 [51] Int. Cl "1101] l/96, HOlj 19/50 [58] Field of Search ..3l3/283285, 220

[56] References Cited UNITED STATES PATENTS 8/1947 Cartun ..3l3/285 x 9/1939 Marden ....313/283 UX l/1967 Deshaw ..313/285 X 8/1947 Cartun ..313/285 X FOREIGN PATENTS OR APPLICATIONS 440,138 12/1935 Great Britain ..3l3/283 1,557,527 1/1969 France ..3l3/283 Primary Examiner-David Schonberg Assistant Examiner-T. H. Kusmer Attorney-Frank R. Trifari I57] ABSTRACT The invention relates to a discharge lamp provided with a substantially straight oblong discharge tube and an outer envelope surrounding this tube.

The invention provides a solution in which a simple positioning of the discharge tube in the outer envelope can be obtained with the aid of an elongated part of the terminal wire. This solution is combined with an anti-shadow winding of that part of the terminal wire, which extends along the straight part of the discharge tube. By using this anti-shadow winding there need not be the risk of cracks in the outer envelope as a result of expansion of the terminal wire (by heat produced in the discharge tube).

3 Claims, 2 Drawing Figures PATENTEU 3.706801 INVENTOR. GERARD M.J. DE NEVE 2% 6 AGENT DISCHARGE LAMP PROVIDED WITH A SUBSTANTIALLY STRAIGHT OBLONG v DISCHARGE TUBE The invention relates to a discharge lamp provided with a substantially straight, oblong discharge tube and an outer envelope surrounding this tube, a convolute part of a terminal wire constituting a centring member of the discharge tube and at least a portion of the convolute part of the terminal wire bearing upon the inner side of an end part of the outer envelope.

A discharge lamp of the kind mentioned above is described, for example, in United Kingdom Pat. specification No. 440,138. For obtaining a good resilient support of the discharge tube relative to the outer envelope the convolution in this known lamp is rather elastic. It is true that this construction provides a satisfactory resilient support thereby, but a disadvantage is that during the manufacture it is difficult to give the discharge tube a very defined position in the outer envelope. (A method of giving a lamp part a very defined position is sometimes referred to as positioning.) In fact, when in the manufacture of a lamp of the known type only the mentioned convolute part of the terminal wire would be used for positioning, a discharge tube of one specimen, when introduced into an outer envelope, would sag into this outer envelope farther than another discharge tube of the same type. This is a drawback because further steps should then have to be taken to obtain a satisfactory positioning.

An object of the present invention is to render a simple centration of the discharge tube in the outer envelope possible in a discharge lamp of the kind described, while the centring device also ensures a satisfactory positioning during manufacture.

It is true that there are other solutions for centring an end part of the discharge tube in an outer envelope while also obtaining a satisfactory positioning but in that case a discontinuity is to be provided previously in the head of the outer envelope in order to receive an end part of the terminal wire; see, for example, French Pat. specification No. 1.557.527 (FIG. 1).

According to the invention a discharge lamp provided with a substantially straight, oblong discharge tube and an outer envelope surrounding said tube in which a convolute part of a terminal wire constitutes a centring member of the discharge tube, and in which at least a portion of the convolute part of the terminal wire bears upon the inner side of an end part of the outer envelope is characterized in that substantially the entire convolute part of the terminal wire near the end part of the outer envelope bears against the inner side of said end part, the part of the terminal wire extending along the straight part of the discharge tube being bent in such a manner that its center of gravity is located alongside the terminal wire and in which the center line of the last-mentioned part of the terminal wire can only have tangents which constitute an angle of less than with the longitudinal axis of the lamp.

An advantage of this lamp is that the convolution can be formed in a fairly rigid manner so that a satisfactory positioning of the discharge tube in the outer envelope is possible in a very simple manner. In fact, the discharge tube together with the terminal wire is simply lowered into the outer envelope until the convolution bears against the outer envelope. A further advantage of the lamp according to the invention is that the outer outwards.

envelope cannot crack when the temperature is increased (for example, when the lamp is switched on) because the terminal wire which extends along the straight part of the discharge tube can bend to some extent. An additional advantage is that the entire con struction of the terminal wire may be fairly rigid due to the fairly small angle constituted by the terminal wire with the axis of the lamp.

It is feasible, for example, that the end part of the outer envelope is formed as a disc which is at right angles to the longitudinal axis of the outer envelope. In that case the convolution of the terminal wire is also in a plane at right angles to this longitudinal axis.

In a special embodiment of a discharge lamp according to the invention in which the end part of the outer envelope substantially has the shape of a concave hemisphere, the center line of the convolute part of the terminal wire located near the end part of the outer'envelope is substantially located in a flat plane containing the longitudinal axis of the lamp.

An advantage of this embodiment is that a shape of the outer envelope which is handy in practice can be accompanied by a simple shape of the convolution while no sharp corners are present in the terminal wire.

It is feasible that the part of the terminal wire extending along the straight part of the discharge tube consists of two straight pieces enclosing an angle. In that case, the center of gravity of this portion is also outside the terminal wire and these pieces of the terminal wire can be expanded upon heating because they can be bent In an advantageous embodiment of a discharge lamp according to the invention, the part of the terminal wire extending along the straight part of the discharge tube is helically bent and has a pitch which is approximately three times the length of the discharge tube.

An advantage of this embodiment is that the influence of the terminal wire on the distribution of the light is very slight. In fact, due to thisvwound terminal wire (anti-shadow winding) the influence of this terminal wire on the light being emitted into a certain direction is only slight.

In order that the invention may be readily carried into effect, an embodiment thereof will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:

FIG. 1 shows a discharge lamp according to the invention, and

FIG. 2 is a longitudinal section through an end part of the lamp of FIG. 1.

In FIG. 1, the reference numeral 1 denotes a glass outer envelope of a high-pressure sodium vapor discharge lamp. This is a lamp of approximately 400 Watts having a length of approximately 27.5 cms. The reference numeral2 denotes lamp cap; the reference numeral 3 denotes a discharge tube in the outer envelope 1. The reference numeral 4 denotes a pinch through which two electric supply conductors 5 and 6 extend. The supply conductor 5 is connected to a conductor 7 which is loosely inserted on the other side into a tubular current supply member 8 which is provided at one end of the discharge tube 3. A stranded wire 9 is secured to the conductor 7 which wire is in electrical contact with the outer circumference of the current supply member 8. The supply conductor 6 is connected to a terminal wire which consists of a helical part and a convolute part 11. A rigid current supply strip 12 which is connected to a tubular current supply member 13 of the discharge tube 3 is secured to the portion of the helical part 10 facing the convolute part 11. The convolution 11 bears against the semi-convex end part of the outer envelope 1. This can be seen more clearly in FIG. 2. FIG. 2 shows a portion of the lamp of FIG. 1 in which the outer envelope 1 is intersected. The same reference numerals in FIG. 2 and FIG. 1 relate to the same components.

In one embodiment the diameter of the outer envelope l was 4.6 cms and the diameter of the discharge tube 3 was 0.95 cm. The length of the discharge tube 3 was approximately I 1.5 cms. The terminal wire '10 and the convolution ll consisted of nickel including a small addition of manganese. The thickness of the wire was approximately 2 mms. A tangent to the center line of the wire 10 constituted a maximum angle of with the longitudinal axis of the lamp. (The center line of the wire is understood to mean the line which is constituted by the centers of the cross-sections of this wire). The pitch of the wire 8 was approximately 35 cms, thus approximately three times the length of the discharge tube 3.

In the given construction the positioning of the discharge tube 3 in the outer envelope 1 is simple, for the combination 3 to 13 inclusive is slid into the outer envelope 1 until the convolution 11 engages the round end part of this outer envelope. When using this construction it need not be feared that damage of the outer envelope will occur when the lamp is switched on, for the terminal wire piece 10 will expand when heat is generated in the discharge tube but due to its so-called anti-shadow winding, namely the helical form in which it is bent, this expansion only causes this piece of wire terminal 10 to be bent out further. The convolution 11 also serves as a centring member. I

In summary it may be stated that the construction described leads to a discharge light source whose discharge tube can be satisfactorily positioned in a simple manner and in which the risk of damage of the outer envelope by fluctuations in temperature is only small.

What is claimed is:

l. A discharge lamp provided with a substantially straight, oblong discharge tube and an outer envelope surrounding said tube in which a convolute part of a terminal wire constitutes a centring member of the discharge tube, wherein substantially the entire convolute part of the terminal wire near the end part of the outer envelope bears against the inner side of said end part, the part of the terminal wire extending along the straight part of the discharge tube being bent in such a manner that its center of gravity is located alongside the terminal wire and in which the center line of the last mentioned part of the terminal wire can only have tan? gents which constitute an angle of greater than 0 but less than 25 with the longitudinal axis of the lamp.

2. A discharge lamp as claimed in claim 1, in which the end part of the outer envelope substantially has the shape of a concave hemisphere, wherein the center line of the convolute part of the terminal wire located near the end part of the outer envelope is substantially located in a flat plane containing the longitudinal axis of the lamp.

3. A discharge lamp as claimed in claim 1 charac- 

1. A discharge lamp provided with a substantially straight, oblong discharge tube and an outer envelope surrounding said tube in which a convolute part of a terminal wire constitutes a centring member of the discharge tube, wherein substantially the entire convolute part of the terminal wire near the end part of the outer envelope bears against the inner side of said end part, the part of the terminal wire extending along the straight part of the discharge tube being bent in such a manner that its center of gravity is located alongside the terminal wire and in which the center line of the last mentioned part of the terminal wire can only have tangents which constitute an angle of greater than 0* but less than 25* with the longitudinal axis of the lamp.
 2. A discharge lamp as claimed in claim 1, in which the end part of the outer envelope substantially has the shape of a concave hemisphere, wherein the center line of the convolute part of the terminal wire located near the end part of the outer envelope is substantially located in a flat plane containing the longitudinal axis of the lamp.
 3. A discharge lamp as claimed in claim 1 characterized in that the part of the terminal wire extending along the straight part of the discharge tube is helically bent at a pitch which is approximately three times the length of the discharge tube. 